<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Output</title>
</head>
<body>

<form oninput="x.value=parseInt(a.value)+parseInt(b.value)">
    0<input type="range" id="a" value="50">100
    + <input type="number" id="b" value="50">=
    <output name="x" for="a b"></output>
</form>

</body>
</html>